S ymphytum ibericum Steven: LC–HRMS/MS-based phytochemical profile, in vitro antioxidant and enzyme inhibitory potential

Abstract

Background: Symphytum L. (comfrey, Boraginaceae) has a longstanding use as a remedy to alleviate the clinical symptomatology in arthritis, strains, contusions or sprains. In the recent years, considerable research efforts were put into assessing the chemico-biological profile of unexploited Symphytum species, with the aim to extend the medicinal valences of the genus to new pharmacological applications. However, to date there are no previous comprehensive phytochemical characterization and multi-biological evaluation of S. ibericum Steven, a perennial Boraginaceae plant distributed in the Northeastern Turkey and Caucasus region. Results: Total phenolic and flavonoid content of extracts obtained from the leaves and roots of S. ibericum varied between 10.53 ± 0.20 to 84.95 ± 0.60 mg gallic acid equivalents/g and between 0.81 ± 0.06 to 20.88 ± 0.29 mg rutin equivalents/g. The liquid chromatography hyphenated with tandem high-resolution mass spectrometry (LC–HRMS/MS)-based phytochemical profiling revealed a number of 29 distinct compounds, such as phenolic acids (e.g., caffeic acid, rosmarinic acid, globoidnan B, rabdosiin, globoidnan A), flavonoids (e.g., quercetin derivatives, luteolin, apigenin), pyrrolizidine alkaloids (e.g., intermedine–N-oxide, lycopsamine-N-oxide, symphytine-N-oxide), organic and oxygenated unsaturated fatty acids. The evaluation of the antioxidant activity showed potent scavenging activity against synthetic radicals, cupric ion reducing (37.60 ± 0.15–436.26 ± 7.12 mg Trolox equivalents/g), ferric ion reducing (21.01 ± 0.74–229.99 ± 3.86 mg Trolox equivalents/g) and chelating capacity; in general, the leaf extracts displayed superior antioxidant effects than the corresponding root extracts. With respect to the inhibitory activity tested on various pharmacologically relevant enzymes, interesting anti-acetylcholinesterase (0.32 ± 0.03–3.32 ± 0.12 mg galanthamine equivalents/g), anti-butyrylcholinesterase (0.88 ± 0.06–5.85 ± 0.16 mg galanthamine equivalents/g) and anti-tyrosinase (21.84 ± 0.21–61.94 ± 2.86 mg kojic acid equivalents/g) properties were noticed. Exploratory multivariate analysis revealed four clusters with respect to phytochemical profile, of which one rich in danshensu, quercetin hexoside, dehydrorabdosiin, dihydrogloboidnan B and quercetin acetylhexoside. Conclusions: As evidenced through the phytochemical characterization and multi-biological evaluation, S. ibericum can be regarded as a prospective source of pharmaceutical or cosmeceutical ingredients with putative uses in the management of chronic conditions linked to oxidative stress, such as Alzheimer’s disease or skin pigmentation disorders. Graphical Abstract: [Figure not available: see fulltext.]